The planets are always moving around the zodiac.
As they make angles (aspects) to places where planets Were when you were born, things will Tend to happen in your life. This section lists what each individual aspect means. Several possibilities are listed for each transit since they can work out in different ways, depending on the context of your birth chart, and, of course, your stage of life. Transiting Uranus making a conjunction with the natal position (the placement in the birth chart) of Venus will not produce a love affair in the horoscope of a two-year old. Nor will Jupiter crossing the Mid-Heaven of a homeless drug addict suddenly produce “advancement in career”.
Another word of warning. Never try to make a forecast based on just one factor alone. Look at them all because you never can tell. Beginners always make that mistake (and even some practicing astrologers!). That Jupiter aspect you were counting on to increase your money may be canceled out by that accident aspect between Uranus and Mars. Be sure to Check everything before making that forecast.
Progressions are calculated as follows. Each day after your birth is taken as being equivalent to one year of your life. For example, if you want to find your progressions for when you were 15 years old, you would calculate a new horoscope for 15 Days after your were born (same year, same place of birth, and same time of day). That will be your Progressed Horoscope for age 15.
Then, you check to see if there are any aspects in the progressed chart that are within one degree of being exact. You also compare the progressed chart with your birth horoscope to see if any of the progressed planets are making aspects to your birth planets. Again, all aspects must be within one degree of being exact. These will be the aspects that will influence you during that time. And they can influence you for a long time.